The paper presents the results of research on a patented, new mixer design with a large blade pitch (p/D ≥ 2) operating in a double-sided open diffuser positioned eccentrically in a water tank for various conditions. Mixing was carried out in the turbulent range (Re > 10000). Due to the bidirectional way of feeding the mixer located in the diffuser and the bidirectional way of leaving the diffuser by the mixed liquid, it is possible to generate wandering vortices, by which the mixing power of proposed design is greater than that of conventional impellers. The employment of the diffuser minimize the energy consumption of the design. The research analyzed the time of dissolving a dose of salt as a function of the rotational speed of the mixer and its three-stage position relative to the bottom. The study also examined the mixing power calculated from the current mixer rotational speed and the measured torque on the mixer shaft. The hydrodynamics of the mixing process were investigated using flow markers. Based on dissolution time and calculation, the system efficiencies for all condition are depicted. Investigation was conducted for mixer impellers with four different blade pitches. Finally, the impeller of the most advantageous pitch and position was determined.